The present invention concerns a dosing method for the controllable and continuous generation of carbon dioxide (CO2) and its issue in biologically used systems as well as a set and a reequipment set which make possible the implementation of this method.
In various fields of the maintenance of biological systems there is a need for an even and targeted supply of CO2 over a lengthy period. For example, this is the case in the cultivation or preservation of plants in closed premises, such as for example in greenhouses, and in particular in aqueous systems, for example in ponds or aquaria.
To supply ponds or aquaria with CO2, various processes are known in the prior art.
For example, the supply can be carried out by gas dosing systems from gas cartridges which are pressure charged with CO2. But this method has the drawback that with decreasing gas pressure in the cartridge, the amount of CO2 which is supplied per unit of time continuously decreases without later control of the dosing system. In addition, a CO2 dosing system requires a large amount of space when using gas cartridges and is aesthetically unsatisfactory. This is disadvantageous, especially in the case of ornamental pools and aquaria.
A further known method is the in situ generation of CO2 from a carbonate due to the influence of a mineral acid, which is usually hydrochloric acid in a Kipp""s apparatus. However, such a device can only be operated suitably outside the water which is to be supplied, and it is therefore linked with the same spatial and aesthetic inadequacies as the method which was described above. In addition, the handling of mineral acids such as hydrochloric acid by inexperienced users is not without its problems.
In addition, a method was suggested in which from an effervescent tablet of sodium hydrogen carbonate and citric acid CO2 is released in doses by the slow addition of water. The disadvantage of this method is that with a slow supply of water in a short time an impermeable citrate layer is formed on the effervescent tablet, which impedes a further reaction. Thereby the continuous generation of CO2 can only be ensured for a short period of a few days.
To overcome the problems named above, a method is made available which makes possible the controlled generation of CO2 which is constant over a long period, i.e. a method for the .continuous long term dosing of CO2 in media which are used biologically, comprising the steps below:
i) expulsion of an aqueous acid solution from a storage container by means of a chemical reaction generating gas pressure,
ii) dripping the acid solution into a solid and/or liquid carbonate or hydrogen carbonate composition, and
iii) supplying the resultant CO2 to the medium in use biologically.
In addition, the object above is achieved by the set made available in accordance with the invention for implementation of the process, which comprises a storage container (1), a unit amount of a carbonate or hydrogen carbonate or a mixture of two or more such compounds and a storage container (2) to be placed thereon or therein for the aqueous acid solution with an exit aperture, which permits the dripping into the (hydrogen) carbonate or its solution; and which is charged with a composition which comprises (i) a solid water soluble acid, (ii) a water soluble and preferably solid compound, which can be catalytically decomposed with the development of gas, and (iii) a catalyst.
In addition, a reequipment set is used to solve the problem above, which comprises the necessary initial substances for carrying out the method as well as replacement parts of the apparatus which is used. More precisely, the reequipment set of the present invention comprises a unit amount of a carbonate or hydrogen carbonate or a mixture of two or more such compounds and a storage container (2) for the aqueous acid solution with an exit aperture, which permits the dripping into the carbonate solution, and which is charged with a composition, which comprises (i) a water soluble acid, (ii) a compound which can be decomposed catalytically with the development of gas, and (iii) a catalyst.
Additional aspects and preferred features of the invention are defined in the appended claims. It will be appreciated that where a preferred feature is described or defined with respect to one aspect of the invention, it is equally applicable to other aspects of the invention without requiring explicit mention thereof.
The method in accordance with the invention for the continuous dosing of CO2 has the following steps:
i) expulsion of an aqueous acid solution from a reserve container by means of a chemical reaction which generates gas pressure,
ii) dripping the acid solution into a solid and/or liquid carbonate or hydrogen carbonate composition and
iii) supplying the resultant CO2 to the biologically used medium.
The following advantageous effects are achieved by this method and by the sets and reequipment sets which are used for its implementation:
the release of CO2 is carried out economically and in the smallest space.
A large amount of CO2 can be stored in the initial substances and can be issued over a lengthy period.
The generation of CO2 can be adjusted in accordance with the requirement of the user and it is constant over a long period.
In aquaria, the CO2 can be issued into the water without hose connections, and without impurities with other substances resulting.
The reference to xe2x80x9ccarbonatexe2x80x9d or to xe2x80x9ccarbonate solutionxe2x80x9d also includes in following hydrogen carbonates and all their solutions, to the extent that nothing else is stated.
The above named aqueous solution of an acid can be a solution of any discretionary acid, which is in a position to form an adequately stable aqueous solution, and which is also suitable to release CO2 by reaction with a carbonate or its aqueous solution. Preferably the acid which is used is a solid compound in its pure form, from which the aqueous solution is only produced directly before use.
Equally it is preferred that due to the reaction of the acid with the carbonate, a salt is formed, the solubility of which is so high that it does not precipitate out of the aqueous mixture, which is formed by dripping the acid solution into the carbonate or its solution. Moreover, mixtures of two or more acids can be used.
The carbonate in which or in the solution of which the aqueous acid solution is dripped is a discretionary carbonate or hydrogen carbonate compound. As stated above, it is preferable that the salt which results from the reaction with the acid which is dripped in remains dissolved. Mixtures of two or more carbonate compounds can also be used.
In addition, preferably both the initial compounds as well as the resultant salt should be unproblematic as to health and ecology, and the amount of CO2 which can be released therefrom, based on the weight of the initial substances, should be as large as possible.
Carbonate compounds which are to be used for preference are the carbonates and hydrogen carbonates of the alkali metals, and special preference is given to sodium hydrogen carbonate.
An acid used with special preference is citric acid.
The named components have moreover the advantages that they are economically obtainable and are easy to store and to transport.
The gas pressure generating reaction which is used to expel the acid solution from the storage container is the reaction of a compound which is dissolved or suspended in the aqueous acid solution with the release of a gaseous reaction product. Preferably this concerns the decomposition of a metastable compound, e.g. a peracid compound, such as hydrogen peroxide or derivates thereof. Mixtures of two or more compounds which are compatible with each other can also be used.
The decomposition can be catalyzed by a suitable catalyst. Due to suitable dosing of the catalyst, the amount of the gas volume which is generated can be adjusted per unit of time and therefore the expulsion speed of the acid solution can be exactly adjusted within a broad range. Here it must be taken into consideration that the temperature of the surrounding system has an influence on the reaction speed of the catalyzed reaction. Therefore in warmer environments, such as, for example, tropical aquaria, smaller amounts of catalyst are necessary to achieve the same amounts of gas per unit of time than in colder media.
In addition it is also possible to introduce the catalyst totally or partially directly before the use in the acid container. Thereby the output speed of the acid solution and thereby the amount of CO2 generated per unit of time can be adjusted individually by the user.
Any of the compounds which are known in the prior art as decomposition catalysts are suitable as the catalysts, which A have the effect of catalytic decomposition of the above named compounds, with the generation of gaseous products. When using H2O2 or peroxide compounds, MnO2 or platinum is a preferred catalytic material, with special preference for ceramically bound MnO2. Mixtures of two or more catalysts which are compatible with each other can also be used.
Preferably the composition of the components in the storage container is adjusted at the start of the process in accordance with the invention so that the gas volume which results from the reaction which generates the gas pressure is adequate to expel the entire aqueous acid solution from the storage container. At the same time, the amount of the component which is to be decomposed to form the gaseous products should be dimensioned so that the total acid solution is issued at almost constant expulsion speed from the storage container. The amounts which are necessary and/or suitable for this purpose can be varied depending on the specific form of the system which is used. However, mix ratios of 0.01 to 0.03 mole of the compound to be decomposed to 1 mol of the acid to be expelled have been found to be suitable.
The gaseous CO2 which results from dripping the acid solution into the carbonate or its solution, is supplied via suitable gas line devices to the media which are used biologically. In the case of aqueous biological media such as, for example, ponds or aquaria, the CO2 can preferably be in contact with the water surface by means of a diving bell and can be diffusively dissolved in the water via this bell. What is meant here by the water surface is both the surface of the water to be supplied as well as an artificially generated water surface within the water below the diving bell, which is in contact with the gas volume of a device which is suitable to carry out the method in accordance with the invention.